Can the black and white holes combine? - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.

A black hole is a region of spacetime from which gravity prevents anything, including light, from escaping.

(From Wikipedia)

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A white hole, in general relativity, is a hypothetical region of spacetime which cannot be entered from the outside, but from which matter and light have the ability to escape.

(From Wikipedia)
The characteristics of these two kinds of wholes are opposite to each other. I would like to know can they combine when colliding to each other? The Black hole cannot enter the white one (since the latter does not accept anything) but the white hole can approach to the black hole and enter there. Is it possible? What kind of space object would be created at such collision? Maybe grey hole?